Note: Some badges are awarded based on score. The term score means the total number of upvotes minus the total number of downvotes.

Any badge with a *** next to it is one of 20 badges that count towards the candidate score displayed on a moderator candidate in an election. The candidate score is a total of 40 points: the first 20 are awarded based on the user's rep divided by 1000 and rounded down; the second 20 represents the total number of unique badges earned of the 20 that count. Note that if the same badge is earned multiple times, it will only count once towards the candidate score.

9 Answers
9

Question Badges

Altruist

Manually awarding means manually selecting a bounty winner; letting the system auto-award half the bounty does not count (source).

Not awarded on per-site metas, since those sites do not have bounties.

Benefactor

bronze; awarded once

Award a bounty on your own question

Manually awarding means manually selecting a bounty winner; letting the system auto-award half the bounty does not count (source); letting the system auto-award the full bounty to an accepted answer does not count either.

Not awarded on per-site metas, since those sites do not have bounties.

Curious

bronze; awarded once

Asked a well-received question on 5 separate days, and maintained a positive question record

Inquisitive

silver; awarded once

Asked a well-received question on 30 separate days, and maintained a positive question record

Socratic

gold; awarded multiple times

Asked a well-received question on 100 separate days, and maintained a positive question record

Additional criteria for this badge family:

There are four different counts that are tracked when calculating the criteria for this badge:

Positive: Number of questions asked on this day that have a score greater than 0.

Negative: Number of questions asked on this day that have a score less than 0.

Closed: Number of questions asked on this day that are currently closed and the current closure date occurred within 60 days of being asked.

Deleted: Number of questions asked on this day that are currently deleted and the current deletion date occurred within 60 days of being asked.

Any day that has at least 1 Positive question and also has no Negative, Closed, or Deleted questions counts as a GoodDay which increments the counter.

A positive question record means you don't have too many closed, downvoted or deleted questions, overall. The formula is (TotalQuestions - Negative - Closed - Deleted) / TotalQuestions ≥ 0.5. Questions that qualify as Negative and Closed and Deleted count three times in this calculation!

Favorite Question

silver; awarded multiple times

Have a question listed as a favorite by 25 users

Stellar Question

gold; awarded multiple times

Have a question listed as a favorite by 100 users

Investor ***

bronze; awarded once

Offer a bounty on another user's question

Not awarded on per-site metas, since those sites do not have bounties

Nice Question

bronze; awarded multiple times

Earn a score of 10 on one question

Good Question

silver; awarded multiple times

Earn a score of 25 on one question

Great Question

gold; awarded multiple times

Earn a score of 100 on one question

Popular Question

bronze; awarded multiple times

Receive 1000 views on one question

Notable Question

silver; awarded multiple times

Receive 2500 views on one question

Famous Question

gold; awarded multiple times

Receive 10,000 views on one question

Promoter

bronze; awarded once

Offer a bounty on your own question

Not awarded on per-site metas, since those sites do not have bounties

Scholar

bronze; awarded once

Accept an answer

Student

bronze; awarded once

Receive a score of one on a question

Tumbleweed

bronze; awarded once

Ask a question that after its first 7 days of existence has a score of 0, no answers, no comments, and no more than 60 views.

Note that the badge is still awarded if the question has as many upvotes as it does downvotes; it doesn't necessarily need to have no votes at all.

Tag Badges

What are tag badges?

Users may earn badges on any site for positive contributions to established tags used on that site. Each tag badge has the same name as the tag for which it was awarded.

When a user meets the requirements for a tag badge that has never been awarded, the system creates and awards it automatically. These badges are displayed with a white background, unlike other badges that are displayed with a black background.

Tag badges that are no longer applicable are revoked, unlike "regular" badges.

A tag must appear on a minimum of 100 questions to be considered for tag badges.

What is a tag score?

A tag score is basically the combined total of all the upvotes (+1) and downvotes (-1) you've accumulated on answers under that specific tag (votes on questions do not count). As well, posts which are in community wiki status or that have been deleted do not count towards your tag score. Tag scores are only recalculated once daily, at 03:00 UTC.

Bronze

100 total score

only non-wiki / non-deleted answers count

minimum of 20 answers on the tag to be considered

Silver

400 total score

non-wiki non-deleted answers

minimum of 80 answers

Gold

1000 total score

non-wiki non-deleted answers

minimum of 200 answers

Possessing a gold badge for a tag will allow you to cast binding votes to close questions as duplicates or reopen questions closed as duplicates, provided you haven't edited the tags or previously voted to close or reopen, respectively. Source

Unlike most other badges, tag badges are revoked immediately if you ever cease to meet their criteria, which can happen if your answers are downvoted, deleted, or converted to community wiki, if the tag is removed from questions that you've answered, or if the tag becomes ineligible for badges because it's no longer used on 100+ questions.

Upholder

In revision 103 text was edited. So, do duplicate questions count as “well-received” for the Curious this days?
– SuvitrufJan 13 at 0:00

@Suvitruf It's likely you noticed it counting because questions that are closed more than 60 days after being asked aren't considered "closed" for the purposes of the badge. (P.S. you posted your comment on the wrong answer)
– Sonic the Inclusive HedgehogJan 21 at 22:59

@SonictheIntrovertedHedgehog you are with us again. Glad to see you ^^"
– SuvitrufJan 22 at 3:47

Critic

Custodian

The review doesn't necessarily have to take place via /review. That means users with low reputation are able to gain this badge, when reviewing a suggested edit on one of their own posts.

Reviewer ***

silver; awarded once per review task

Review 250 posts in a review task

Replaces Reviewer (old) - see below

Reviewer (old)

silver; awarded once; retired

Already possess the Strunk & White badge

Review at least 1000 posts from the review section or flag queue

Take action on at least 200 posts from the review section or flag queue

For the purposes of the badge, actions include

Editing successfully (i.e. declined edit suggestions do not count)

Flagging helpfully

Successfully voting to close

Voting on the post, unless the post gets deleted

Commenting on the post

Proposed at two levels: silver at 1000 reviews/300 actions and bronze at 300/60. Initially introduced as a bronze badge with the 300/60 requirement, but was changed to silver at 1000/200 approximately one day later.

Replaced with Custodian, Reviewer (see below), and Steward on September 21, 2012 (source)

Users who already had this badge will have an extra silver Reviewer badge, but it can no longer be attained

Steward ***

gold; awarded once per review task

Review 1,000 posts in a review task

Disciplined

bronze; awarded once

Delete one of your own posts that has a score of three or more at the time of deletion

Posts that you own but are not self deleted do not count.

Editor

bronze; awarded once

Edit the title or body of any post (including your own, excluding grace period edits)

Strunk & White ***

silver; awarded once

Perform a total of 80 edits between questions, answers, and tag wikis

Copy Editor ***

gold; awarded once

Perform a total of 500 edits between questions, answers, and tag wikis

Edits you suggest before gaining full edit privileges do count, once approved (source)

Each edited post counts only once, regardless of how many additional edits you may submit

Electorate ***

gold; awarded once

Vote on 600 questions

Have at least 25% of your total number of votes cast (questions and answers) be on questions

Comment votes do not count

Answer votes do not count

Votes cease to count if the questions get deleted

This seems to be an especially confusing badge, so here are some examples to address cases commonly complained about on MSO. Total is just the total number of votes cast (Questions + Answers) and Ratio is the total number of votes cast that are on questions.

Taxonomist

If User A creates a tag that falls into disuse and User B later uses the tag again, User A continues to get credit for creating the tag, for the purposes of this badge (source)

Vox Populi

bronze; awarded once

Cast 40 votes - the maximum (limit) for a single day.

Each "day" lasts from midnight UTC to immediately before midnight, UTC; days are not counted in local time

It is possible for the system to restrict you to fewer than 40 votes in a day.

You get two types of votes per day: ten can be used only on questions ("Q-votes") and 30 can be used on either questions or answers ("QA-votes").

When you vote on a question, the system tries to use your Q-votes before your QA-votes.

When you only have five QA-votes left for the day, you can no longer use your Q-votes. The "You have n votes left today" counter starts to appear after you cast votes. This means that if you start a day by voting mostly on answers and burning through your QA-votes first, it'll be impossible for you to reach 40 votes that day.

Fanatic

The exact amount of activity required to count as a visit is not public information

Each "day" lasts from midnight UTC to immediately before midnight, UTC; days are not counted in local time

Mortarboard

bronze; awarded once

Earned at least 200 reputation in a single day

Epic

silver; awarded once

Earned at least 200 reputation on 50 days

Legendary

gold; awarded once

Earned at least 200 reputation on 150 days

Additional criteria for this badge family:

All of the following events count towards a specific day's total reputation calculation: upvotes and unupvotes, accepts (both to the asker and the answerer) and unaccepts, suggested edit approvals, bounties earned, and documentation reputation events (on Stack Overflow).

Any other events like downvotes, the association bonus, vote invalidations, and deletions are not considered.

Votes that are later deleted for any reason (manually retracted or invalidated) do not affect previous days' reputation earned calculation. Unupvotes and unacceptes affect the day the undo event occurred.

Each "day" lasts from midnight UTC to immediately before midnight, UTC; days are not counted in local time.

Precognitive

bronze; awarded once

Awarded to those who followed the Area 51 proposal for a particular Stack Exchange site before it entered the commitment phase, when the site enters its private beta phase.

In other words, it marks the people who have been around and supported the site before it was even launched

Not attainable on all sites; in particular, those that were launched before the Area 51 site creation process was invented, like Stack Overflow, Super User, and Server Fault

Beta

All three requirements must be met, and met before the public beta begins (or possibly before the badge script runs)

Not awarded on Meta sites, including Meta Stack Exchange

Quorum ***

bronze; awarded once

One post with score of 2 or more on the related meta site

Not available on Stack Apps as it doesn't have a meta site

Convention ***

silver; awarded once

Post at least 10 posts which each have a score of 2 or more on the related meta site

Additional criteria for this badge family:

By definition, not available on meta sites, including Meta Stack Exchange

Not available on Stack Apps

Talkative

bronze; awarded once

Post at least ten messages in chat

Receive at least one star in chat

Chat messages in private rooms also count for this badge

Outspoken

silver; awarded once

Receive stars from at least ten different users for at least 10 different messages in chat

Each message is only counted once, and each user is only counted once. So it’s not enough if one message is starred by nine people, and a tenth user stars nine other messages.

If you want to know, here’s the precise definition: Consider the bipartite graph whose vertices are all your messages and all the users, and whose edges are the stars you received. So a user (vertex) and a message (vertex) are connected by an edge if and only if the given user has starred the given message. You are eligible for the Outspoken badge if and only if this graph has a matching number of at least ten.

Yearling ***

silver; awarded multiple times

Have a reputation of at least (number of years since registration) × 200 + 1 (starting reputation)

The number of years is not restricted to integers and increases continuously. For example, if at the 2-year mark you don’t have the 400 required reputation, the number of years still continues to increase. So half way through year 3 (i.e., after 2.5 years), you’d need 2.5 × 200 = 500 reputation to qualify for the second yearling badge.

You can be awarded only one badge each time the script runs; if you find yourself suddenly qualifying for multiple badges, expect to get one each time the script runs until you're caught up.

Other Badges

Analytical

As of June 2013, this badge is no longer awarded due to the FAQ being changed to the Help Center all across the network. Those who earned it previously get to keep it.

Visit every section of the FAQ

You may still see users being awarded the badge; those users get it by merging an older account with the badge into a newer account without it

Announcer

bronze; awarded multiple times

Share a link to a question or answer that is visited by 25 unique IP addresses

Booster

silver; awarded multiple times

Share a link to a question or answer that is visited by 300 unique IP addresses

Publicist

gold; awarded multiple times

Share a link to a question or answer that is visited by 1000 unique IP addresses

Additional criteria for this badge family:

The date that the post was created is irrelevant

In order to get credit for a certain click, the link must be a short-form link that contains your user ID (e.g. https://$site/[q|a]/[post ID]/[user ID]). Short links that don't contain the "user ID" portion and full-form links don't count. If you want to be sure a particular link counts, use the "share" button underneath the post.

Prior to early 2017, only links from outside the Stack Exchange network counted. This was changed for technical reasons as a result of the changeover to HTTPS, and was awarded retroactively.

Census

For the 2017 and 2018 iterations of the Developer Survey, the badge could only be earned on Stack Overflow.

For the 2019 Developer Survey, users have the option to earn the badge on a selection of technical sites other than Stack Overflow. After completing the survey, the user will be prompted to choose which one site to award the badge on.

The decision to revoke the badges is explained in this post, excerpt below:

We also have a longstanding policy against revoking badges. But we've never had a badge set for a discontinued beta feature either. While we could just retire them, it seems confusing to show expired Documentation features on the list of badges. In addition, we'd lose a lot of good names for potential future badges. As a compromise, anyone who earned a Documentation badge other than Educated (for reading the tour) will be issued a newly minted silver Documentation Beta badge.

Renovator

Why didn't I get badge name right now?

(even though the badge progress tracker on my user profile or the review stats page indicates that I qualify for the badge; I even got the message "Congratulations - you earned badge name")

Most badges (with the exception of the Informed badge) are awarded by a scheduled job which runs once every hour and are non-deterministic, i.e. there is no guarantee that your badge will be awarded within an hour.

Additionally, if an event occurs during the time between you qualifying for the badge and the scheduled job running that causes you to no longer qualify for the badge, you will not earn the badge. For instance, if you edit and answer a question and your answer gets upvoted, but it gets downvoted back to 0 before the script runs, you won't earn the Explainer badge. If the badge is one that can be tracked in the user profile, it may take some time before it once again shows up as a trackable badge.

Tag badges are based on tag scores, and those are calculated once every day (in the early UTC morning), so tag badges are awarded even less often.

Thank you for your interest in this question.
Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site (the association bonus does not count).